B ISBEE, Ariz. (AP) — Authorities are investigating an apparent assault on a 60-year-old National Park Service female employee in southeast Arizona that left her in critical condition.

The Cochise County Sheriff’s office says the woman was found unconscious Wednesday afternoon in a picnic area restroom in the Chiricahua Mountains, apparently suffering from head trauma.

The office says she was airlifted to a Tucson hospital in critical but stable condition. No other details were released on the extent of her injuries or how she was hurt.

The woman’s government vehicle was missing and authorities located it abandoned in Douglas by tracking her cell phone, which was still inside the vehicle.

Cochise County Sheriff Mark Dannels says deputies are working closely with federal and state law officers to ” identify the suspect(s) who apparently seriously injured a federal employee.” The FBI has joined in the investigation.